Process for impregnating insulating materials



Patented My 26, 1932 UNITED STATES PATENT OFFICE LUIGI EMANUELI, 0F MILAN, ITALY ASSIGNOR TO SOGIETA ITALIANA PIRELIJI, OF MILAN, ITALY PROCESS FOR .IMPREGNATING INSULATING MATERIALS No Drawing. Application filed August 15, 1927, Serial No. 213,173, and in Italy August 31, 1926.

The object of the present invention is a process for obtaining a perfect impregnation with insulating compounds, excluding all traces of air, in any porous material which 5 may form part, for instance, of electrical apparatus.

This process is particularly adapted for impregnating with insulating compounds electric cables for power transmission.

W It is based on the great solubility of some gases in the insulating compound or in the oils used in electrical apparatus and particularly in cable manufacture. Amongst said gases I may mention CO (carbonic acid);

15 (1 H, (propane); (3 H (acetylene) and generally easily liquefying gases.

The above mentioned process consists in the following steps: The material to be impregnated, for example the factory insulation of an electric cable, is first of all thoroughly dried by ordinary methods, and then the air is extracted from the cable as completely as possible; then a gas soluble in the oil to be used for the impregnation, carbonic acid for instance, is admitted and is subsequently extracted with a vacuum pump so that the only traces of gas remaining will be exclusively This gas-washing treatment may subsequently be repeated with more gas to make .sure that after the -vacuum, all the air has absolutely been extracted and only CO remains. Oil is then introduced into the cable at a convenient temperature, this oil'having the oil to be used for impregnation.

cables with liquid insulating compounds, the .steps of extracting the air from the interior For this reason the insulating oil must be previously deprived of gases. This is obtained by special apparatus operating at a. certain temperature and in vacuum.

It is evident that the process here described 5 is particularly convenient for impregnating high-tension cables, but can be used also for cables with any sort of impregnating material. Similarly it can be applied in all cases in which it is desirable to effect impregnatlon with liquid or fluid materials of given parts or apparatus particularly for electric uses so as to obtain a thorough exclusion of air.

The process can be applied with profit in a special manner in the case of electric transformers.

I claim as my invention:

1. In a process of impregnating electric of a cable, washing the evacuated interior of the cable with a gas which is hi hly soluble in the insulatingcompound to 'e used, removing such gas by vacuum action, dcg'asifying the insulating compound, and thereafter introducing the degasified insulating compound into the cable.

2. In a process of impregnating electric cables with liquid insulating compounds, the steps of extracting the air from the interior of a cable, repeatedly'introducing into and removing from the interior-of the cable a washing gas which is highly soluble in the insulating compound to be used, removing such gas by vacuum action, degasifying the insulating compound, and thereafter introducing the degasified insulating compound into the cable. v

3. A process of impregnating electric cables with oil, comprising the steps of thoroughly drying the factory insulation of a cable, extracting the air from the interior of the cable,'washing the evacuated interior of the cable with a gas which is highly soluble in the oil to be used, removing such gas by vacuum action, and introducing the oil into the cable after having first been treated to remove all gases therefrom.

4. A process of impregnating electric cables with oil, comprising the steps of extracting the air from the interior of the cable, washing the evacuated interior of the cable with carbon dioxide, removing the carbon dioxide by vacuum action, degasifying the oil, and thereafter introducing the degasified oil into the cable. 7

5. A process of impregnating porous materials with liquid insulating compounds, comprising the steps of drying thoroughly the material to be impregnated, extracting the air therefrom,-introducing into the evacuated material a gas which is highly soluble in the insulating compound to be used, rem0V- ing such gas by vacuum action, and finally introducin the insulating compound into said material after having first been treated to remove all gases therefrom.

6. A process of impregnating porous materials with liquid insulating compounds, comprising the steps of drying thoroughly the material to be impregnated, extracting the air therefrom, introducing into the evacuated material a gas which is highly soluble in the insulating compound to be used, removing such gas by vacuum action, introducing a fresh quantity of said gas into the said material and extracting it therefrom, and finally introducing the insulating compound into said material after having first been treated to remove all gases therefrom.

7. A process of impregnating porous materials with liquid insulating compounds, comprising the steps of drying thoroughly the material to be impregnated, subjecting the material to a vacuum action to extract the air therefrom, washing the material with a gas which is highly soluble in the insulating compound to be used, removing such gas by vacuum action, and finally introducing the insulating compound into said material after having first been treated to remove all gases therefrom.

8. A cables with liquid insulating compounds, comprising the steps of subjecting-the cable ture, afterwards subjecting the insulated conductor or cable to a vacuum, subsequently subjecting the insulated conductor or cable to the action ofa de-aerated or de-gasified process of impregnating electric to be impregnated to a vacuum action to extract the air therefrom, washing the cable with carbon dioxide, removing the carbon dioxide by vacuum action, degasifying the insulating compound, and thereafter introducing the degasified insulating compound into the cable.

9. In the manufacture of electric cables of the kind'concerned, covering the conductor or cable with a fibrous or porous insulating material constituting the main insulation thereof, subjecting the insulation on the conductor or cable to a gas soluble in an impregnating material used in its manufac- 

